docs: def list_agents(self, **kwargs):
          """List all agents, optionally filtered by a query. Specify filters as
          query keyword argument, such as: 
          
          query= email is abc@xyz.com,
          query= mobile is 1234567890,
          query= phone is 1234567890,
  
          agents can be filtered by state such as:
          
          state=active/occasional
  
          Passing None means that no named filter will be passed to
          Freshdesk, which returns list of all agents 
  
          """
  
          url = 'agents.json?'
          if 'query' in kwargs.keys():
              filter_query = kwargs.pop('query')
              url = url + "query={}".format(filter_query)
  
          if 'state' in kwargs.keys():
              state_query = kwargs.pop('state')
              url = url + "state={}".format(state_query)    
                  
          agents = self._api._get(url)    
          return [Agent(**a['agent']) for a in agents]